linux-kernel - Re: [PATCH v1 08/23] perf perf_regs: Switch from arch string to int e

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Message-ID: <8c1fefd6-4f4c-42a7-9007-5c9df3975080@linux.intel.com>
Date: Wed, 21 Jan 2026 14:58:23 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
 Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
 Adrian Hunter <adrian.hunter@...el.com>, James Clark
 <james.clark@...aro.org>, John Garry <john.g.garry@...cle.com>,
 Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>,
 Guo Ren <guoren@...nel.org>, Paul Walmsley <pjw@...nel.org>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Alexandre Ghiti <alex@...ti.fr>, Shimin Guo <shimin.guo@...dio.com>,
 Athira Rajeev <atrajeev@...ux.ibm.com>,
 Stephen Brennan <stephen.s.brennan@...cle.com>,
 Howard Chu <howardchu95@...il.com>, Thomas Falcon <thomas.falcon@...el.com>,
 Andi Kleen <ak@...ux.intel.com>, "Dr. David Alan Gilbert"
 <linux@...blig.org>, Dmitry Vyukov <dvyukov@...gle.com>,
 Krzysztof Łopatowski <krzysztof.m.lopatowski@...il.com>,
 Chun-Tse Shao <ctshao@...gle.com>, Aditya Bodkhe <aditya.b1@...ux.ibm.com>,
 Haibo Xu <haibo1.xu@...el.com>, Sergei Trofimovich <slyich@...il.com>,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
 linux-riscv@...ts.infradead.org, Mark Wielaard <mark@...mp.org>
Subject: Re: [PATCH v1 08/23] perf perf_regs: Switch from arch string to int
 e_machine

On 1/21/2026 2:49 AM, Arnaldo Carvalho de Melo wrote:
> On Fri, Jan 16, 2026 at 09:28:34PM -0800, Ian Rogers wrote:
>> The arch string requires multiple strcmp to identify things like the
>> IP and SP. Switch to passing in an e_machine that in the bulk of cases
>> is computed using a current thread load. The e_machine also allows
>> identification of 32-bit vs 64-bit processes.
>>
>> Signed-off-by: Ian Rogers <irogers@...gle.com>
>> ---
>>  tools/perf/builtin-script.c                   |  17 ++-
>>  tools/perf/util/evsel.c                       |  14 ++-
>>  tools/perf/util/perf_regs.c                   | 105 +++++++++++-------
> [ Include dwarf-regs.h to get conditional defines for EM_CSKY and EM_LOONGARCH, not available in old distros ]
>
> - Arnaldo

Seems the change would introduce the below building error.

util/perf_regs.c: In function ‘perf_reg_name’:
util/perf_regs.c:48:14: error: ‘EM_LOONGARCH’ undeclared (first use in this
function)
   48 |         case EM_LOONGARCH:
      |              ^~~~~~~~~~~~
util/perf_regs.c:48:14: note: each undeclared identifier is reported only
once for each function it appears in
util/perf_regs.c: In function ‘perf_arch_reg_ip’:
util/perf_regs.c:114:14: error: ‘EM_LOONGARCH’ undeclared (first use in
this function)
  114 |         case EM_LOONGARCH:
      |              ^~~~~~~~~~~~
util/perf_regs.c: In function ‘perf_arch_reg_sp’:
util/perf_regs.c:143:14: error: ‘EM_LOONGARCH’ undeclared (first use in
this function)
  143 |         case EM_LOONGARCH:
      |              ^~~~~~~~~~~~

It looks EM_LOONGARCH is not defined in the <elf.h> header file, not sure
which one is better, include  dwarf-regs.h suggested by Arnaldo or direct
add the define,

diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
index b58d59b84fb1..ce839df19fa3 100644
--- a/tools/perf/util/perf_regs.c
+++ b/tools/perf/util/perf_regs.c
@@ -6,6 +6,10 @@
 #include "util/sample.h"
 #include "debug.h"

+#ifndef EM_LOONGARCH
+#define EM_LOONGARCH           258
+#endif
+
 int __weak arch_sdt_arg_parse_op(char *old_op __maybe_unused,
                                 char **new_op __maybe_unused)
 {

>